on dit vs rumor

on dit

noun
  • A flying report; rumour. 

rumor

noun
  • Information or misinformation of the kind contained in such claims. 

  • A statement or claim of questionable accuracy, from no known reliable source, usually spread by word of mouth. 

verb
  • To tell a rumor about; to gossip. 

How often have the words on dit and rumor occurred in a corpus of books? (source: Google Ngram Viewer )